Many phosphoric esters are known for their insecticide action. One of the best known is O,O-diethyl-O-p-nitrophenyl-phosphorthioate, described in German Pat. No. 814,152 and in U.S. Pat. Nos. 1,893,018 and 2,482,083, known on the market by the trade name of Parathion: ##STR1##
Notwithstanding its great effectiveness as an insecticide, the use of this compound meets with considerable difficulties due to its extreme toxicity for mammiferous animals.
In the class of aryl-phosphor-amidothioates derivatives, less studied than the previous compound, there is known the Zytron or DMPA; O-(2,4-dichlorophenyl)-O-methyl-N-isopropyl-phosphoro-amidothioate of the formula: ##STR2## USED AS A HERBICIDE OR WEED KILLER AND MARKETED BY THE American Dow Chemical Company.
From a search carried out by some authors on similar O-methyl-O-(2,4,5-trichlorophenyl)-phosphoroamidothioates exerting an insecticidal action on flies, it was found that, while a further substitution with Cl on the benzenic nucleus does not lead to any appreciable improvement, a lengthening or increase in molecular weight of the alkyl chain linked to the nitrogen atom causes a lowering of the biological activity against the "Musca domestica" (house fly) (see E. H. Blair et al: in `Agricultural and Food Chemistry` 11 No. 3 (1963) page 237).
Thus, an object of this invention is that of describing a new class of phosphoric esters endowed with a high insecticide activity and having a relatively low toxicity for warm-blooded animals. Still another object is that of describing their method of preparation.
Still another object of this invention is that of describing the method for fighting infestations by noxious insects based on the use of such phosphoric esters.